BltYOZOA AND SPONGES. 
47 
PTILODICTYA—*5/>. 
Pl. 4, fig*. 19 (fig. 20; mag\). 
On slabs of yellow grit; much weathered; and containing en- 
crinites and small bracliiopod shells, are several imperfect casts 
of. a broad leaf-like species. These also show only the flattened 
surface of the median plate, which is marked as usual by 
accretion lines. 
The fronds must have been convex, and of considerable thick¬ 
ness, as is shown by the cavities left in the stone. The cells were 
oblong and close set (as at a), and a strong calcareous vertical 
bar seems to have been present in each cell, reaching nearly to 
its base, occasionally hollow, but generally solid. So at least, 
I interpret the hollows marked so strongly in fig. 5, and of 
which the nature is more distinctly seen in the magnified 
figure (fig. 6.) 
Locality. — (1738). 
AMORPHOZOA. 
The number of fossil forms of this great group has of late 
greatly augmented, so far as Silurian strata are concerned. 
And several genera, hitherto considered of doubtful status, 
have been placed in it. I may instance such genera as Ischa- 
clltes and Receptaculites, and particularly the Scotch fossil 
Amphispongia, a genus related to the modern rock-sponge 
Grantia. To these, too, has been added the great pyriform 
fossil termed Splicer onites pomurn by Prof. Phillips, but which, 
on closer examination, turns out to be a sponge of curious 
compound structure, the exterior covered with mammillar 
protuberances. 
Such a sponge has recently been found by British collectors 
in Caradoc rocks, and I have proposed the term Spharos- 
pongia * for it. The same genus occurs, too, among the Thibet 
* See Memoirs of the Geol. Survey, Scotland, sheet 32, by Messrs. 
Geikie, Howell, and Salter, 1861, p. 136. 
